The long-term objective of the proposed research is to discover how the functions of specific genes are integrated into developmental programs. There are three developmental programs in Drosophila: larval, imaginal and germinal. This laboratory has recently recovered temperature-sensitive mutations in nine genes whose function was known to be essential for imaginal cell development. Analysis of mutations in six of these genes has revealed that the function of all six of these genes is also essential for larval and/or germinal cell development. The consequences of these mutations will be investigated in regards to the general question of how the products of single genes can have different functions in different cells. These ts mutations will be used to manipulate the proliferation of imaginal disc cells in order to continue investigations of the mechanism of transdetermination. Preliminary studies of one of these ts mutations, RW630, have shown that when mutant individuals are raised at a restrictive temperature they develop at a dramatically slower rate than they do at a permissive temperature. Analysis of the pattern of protein synthesis in mutant imaginal discs has revealed a reproducible difference compared to the normal pattern. One of the specific aims of this project is to test the hypothesis that the primary defect caused by the mutation is in the structure of a protein modifying enzyme. This will be done by comparing peptide digests of those polypeptides which are detected in normal cells but not in mutant cells to the polypeptides which are detected in mutant cells but not in normal cells. Another aim is to compare the consequences of this mutation in larval and germinal cells to that found in imaginal cells. This will be done by comparing the pattern of protein synthesis in mutant larval and germinal cells to that in normal larval and germinal cells, respectively. The significance of the proposed research is its potential for leading to the discovery of organizing principles which regulate a simple developmental system. This should facilitate the study of more complex developmental processes such as embryonic development, regeneration and aging in humans.